(Field of the Invention)
The present invention relates to ball bearing retainers or cages used for, for example, spindles of machine tools.
(Description of Related Art)
An angular contact ball bearing used for a spindle of a machine tool is rotated at a high speed. Therefore, a metallic retainer having a high specific gravity is rarely used, and a retainer made of a resin, such as nylon polyamide, PPS (Poly Phenylene Sulfide Resin), PEEK (Poly Ether Ether Ketone), or phenolic resin, which is reinforced by glass fibers, carbon fibers, or the like is used.
In general, an inner diameter restriction type rolling element, guide retainer is used in intermediate and low speed ranges in many cases (for example, Patent Documents 1 to 3 listed below). Patent Documents 1, 2 disclose an inner diameter restriction type ball guide angular contact ball bearing. Patent Document 3 discloses an inner diameter restriction type ball guide retainer. Further, an outer diameter restriction type roller guide retainer is also suggested (Patent Document 4). The rolling element guide retainer is guided by (in contact with) balls which have been quality-controlled to have fine surface roughness with high accuracy, and the inner diameter surface of an outer ring and the outer diameter surface of an inner ring do not need to be finished by grinding, as distinct from an inner ring guide retainer and an outer ring guide retainer. Therefore, a rolling element guide retainer is excellent in cost as compared to an inner ring guide retainer and an outer ring guide retainer.